Preparation of carbonyls of group vib metals



United States Patent 3,100,687 PREPARATION OF CARBONYLS OF GROUP Vlb METALS John H. Wotiz, Mentor, Ohio, assignor to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware No Drawing. Filed Jan. 28, 1960, Ser. No. 5,103 17 Claims. (Cl. 23-403) This invention relates to a new and improved process of preparing a carbonyl of a group VIb metal.

Group VIb metals as referred to in the specification and claims are tungsten, molybdenum and chromium. In contrast to materials such as cobalt or iron carbonyls, chromium hexacarbonyl up to this time has generally been difiicult to prepare. For example, while chromium hexacarbonyl has previously been prepared by the reaction of chromium chloride with phenyl magnesium bromide in the presence of carbon monoxide, the yields often have been undesirably low, e.g., as in the preparation reported in the text Inorganic Syntheses by Mc- Crary (1950) page 156. On the other hand, the carbonyls of tungsten and molybdenum have heretofore been prepared via the use of metallic reducing agents, e.g.,

zmc.

The present invention comprises a new and improved method of preparing hexacarbonyls of group VIb metals, e.g., chromium hexacarbonyl, by reacting together, preferably in the presence of hydrogen, at a superatmospheric pressure and at an elevated temperature, carbon monoxide, ,a source of a group VIb metal, e.g., in the case of chromium either a chromium compound or metallic chromium, iodine or an iodine-containing compound, whether added as such or generated in situ, and a nitrile such as acetonitr-ile (CH ON). By carrying out the reaction in a nitrile the use of a reducing metal such as zinc or magnesium as heretofore considered essential and certain :difiiculties characterizing prior processes -for preparing hexacarbonyls of group VIb metals are avoided in the absence of any reducing metal.

The term nitrile as used in the specification and claims is intended to refer to compounds of the formula R(CN),, wherein n is 1 or 2; R is an alkyl group such as methyl, ethyl, propyl, butyl, or the like; ary-l such as phenyl, or in the case where n is 2, an lalkylene radical such as ethylene, propylene, butylene or the like. Examples of suitable nitriles of this type are ace-tonitrile, which is preferred at present, butyronitrile, benzonitrile, propionitrile, succinonitrile, and the like.

The practice of this invention may be illustrated by the following equation:

0 0 H2 MCla I2 M(C O)e wherein M is a group VIb metal.

In carrying out the present process, there are combined in a pressure-resistant reaction vessel, such as an autoclave, provided with an agitator and temperature control means, a mixture of a source of a group Vlb metal, e.g., a trivalent chromium compound such as a chromium halide compound selected from the group consisting of chromium iodide, chromium chloride and chromium bromide, prefer-ably chromic trichloride, a chromium oxide, e.g., Cr O a divalent chromium compound such as chromous iodide; tungsten hexachloride, molybdenum pentachloride or the like; or chromium, molybdenum or tungsten metals as such. The chromium or other group VIb metal may be employed in the form of an ore, e.g., chromite (FeOr O or other chromium ores.

Iodine is added when the mixture does not also include chromium or other group VIb metal iodide. The iodine 3, 1 00,6 8 7 Patented Aug. 1 3, 1 963 may otherwise be introduced as free iodine, iodine monochloride, ethylene diiodide, alkali metal iodides, i.e., i0- dides of lithium, sodium, potassium or the like, or alkaline earth metal iodides, i.e., iodides of calcium, barium, strontium, or the like, magnesium iodide, aluminum iodide, zinc iodide, or the like, and the nitrile, e.g., acetonitnle, present in an amount sufiicient to dissolve and/or suspend the reactants, using a neutral inert solvent such as hexane or benzene.

These reactants are combined with carbon monoxide and, preferably hydrogen, typically added at intervals to maintain a desired pressure, the ensuing reaction being conducted at a superatmospheric reaction pressure resulting from an initial total pressure of 1000 to 10,000 p.s.i.g. at 30 C.; in certain instances an initial pressure as low as 500 p.s.i.g. may be employed.

The reaction temperature should be maintained within the range from about to 325 C. Preferably, the temperature is of the order of 200 C., e.g., 180 to 240 C. Temperatures below about 150 C. generally result in undesirably low yields.

The amount of nitrile to be employed is dictated by the amount of reactants employed, it generally being desired that at least 3 mols of the nitrile to each mol of metal compound be used, e.g., 1 mol CrCl to 3 mols acetonitrile.

Generally, the amount of hydrogen introduced, when employed, is regulated by introducing suffioient hydrogen to increase the pressure within the reactor preferably about 2000 p.s.i.g. 200 C., in addition to the pressure of carbon monoxide, the over-all gas pressure being controlled to be above 8000 p.s.i.g. 200 C., and preferably about 8000-12,000 p.s.i.g. 200 C., a specifically preferred total reaction pressure being about 10,000 p.s.i.g. 200 C. The weight ratio of carbon monoxide to hydrogen may vary from about 1:0 to 1:1. The carbon monoxide and hydrogen may be added as such or in the form of a mixture such as exists in water gas or synthesis gas.

When reaction is complete, which is generally evidenced by a drop in the reactor pressure corresponding to the utilization of carbon monoxide during the reaction, e.g., a 3000 p.s.i.g. pressure drop being typical, the carbonyl product can be separated in any suitable way, as by steam distillation or sublimation. The hexacarbonyl product such as chromium hexacarbonyl is useful as an intermediate or as a starting material in the preparation of various chromium compounds including difierent chrome organic compounds. In addition, the chromium carbonyl advantageously can be used to plate chromium metal onto metal surfaces by thermal decomposition ot the carbonyl.

The proportions of the reactants may be varied some what. However, it is generally desired to employ at least substantially stoichiometric proportions of carbon monoxide and the group VI'b compound, i.g., chromium compound, preferably chromiumchloride, i.e., at least about 6 mols CO/mol of the group VIb metal compound. It is preferred to use an excess of carbon monoxide. A- sufiicient quantity of iodine, e.g., at least 1 mol of l /mol of CrCl preferably 3:2,whether added as such or generated in situ, is used to efiect the desired reaction. The minimum amount of iodine generally is about 0.1 mol I to 1 mol of the group VIb metal. In the case of tungsten or molybdenum the iodine can be omitted if desired as can the hydrogen. The carbon monoxide is introduced by providing a carbon monoxide atmosphere in the reaction chamber.

While the exact mechanism of the reactions involved is not completely understood, it is believed that the following reactions occur in the case of the preparation of Cr(CO) CHaCN CrCls NaI (soluble) (r I2) 2 EXAMPLE 7 To illustrate recovery of iodine used in the practice of this invention, the steam distillation residue of Example 6 is oxidized by treatment with 100 ml. of concentrated CrIa N O lu le) (or 012) 5 HNO and maintained at 98 C. for four hours. The 20 I 5 3 CrI 21 weight of crude, wet I sublimed is 88.0 g. Upon re- (3) Heat sublimation, 66.0 g. (87% recovery) of I are obtained.

CrIi (Or Ii (4) (Cr 600 Cr(GO)s EXAMPLE 8 CHiCN OHaCN-Ii (co 10 To illustrate recovery of acetonitrile, the original As the foregoing equations indicate, iodine or an iodi liquid portion of the steam distillate of Example 6 is converts CrCla to a a) which then dissociates redistilled. The CH CN-H O azeotrope boils at 75- toCr andI 76 C. and weighs 280.0 g. A recovery of 60.5%

In order that those skilled in the art may more comt it fl i bt i ed, Pletely understand the present invention and the preferred While the specification thus far has referred to the use methods y Which the Same y be Carried intO effect, of chromic chloride as a reactant, the invention also conthe following specific examples are offered. templates the use of other chromium compounds such as EXAMPLE 1 chromic oxide (Cr O When such a reactant is employed, hydrogen and/or another reducing agent is ad- Prepamtmn of g jgf 2O vantageous, e.-g., up to 10 mols of Cr O of carbon. Such 01013 12 F Cr(C 0)i, 200 C. a reaction is illustrated as follows:

a v A two-liter stirred autoclave is charged with 300 ml. C CO+H2 grwo), of CH CN, 32 g. (0.2 mol) of CrCl 76 g. (0.3 mol) CHaCN of powdered I and an additional 200 ml. CH CN, to 10,000 p. 'so wash-dean all scilid rtelactantsl gomdthe sidgs gt the re- EXAMPLE 9 actor. e vesse is t en sea e an urge t ree times e i with short blasts of CO. The vessel is then charged to A two'hter stmixi i l 18 charged with 5400-5600 p.s.i.g. with co. Agitation causes an initial a Carbon-chm 9 mime 1 200 to 400 p.s.i.g. pressure drop. The reaction mixture 76 lodme of acetommle' is then heated to 200 C. At 200 C. the pressure in the puygmg 'Wlth t vessel is charged 52.00 autoclave is approximately 9000 p.s.i.g., varying from wlth smfmg 1S begun the reapnon mixabout 8800 p.s.i.g. to 94 00 p.s.i.g. H is introduced into i 1S heated to 200 HYdIPgCH 15 then introduced the vessel to increase the pressure 1000 p.s.i.g. During 5 genes. of "four chargfa's p l 3.000 over a bhe first hour of reaction, a pmssure drop of 1000 psig period of six hours. Heating is discontinued. After coolis observed; an additional 1000 p.s.i.g. H is charged to mg to room temperature h autoclave ventgi. a restore the original pressure. H is charged in this manthe contents addqd to one htefr Of water dlsimhng ner to the autoclavg three times The reaction time is flask. The flask 1S heated until the steam distillation of 6 to 8 hours. The heat is then turned oif and the re- Cr(.CO)6 appears compicte' The CMCOM" so action mixture is allowed to cool to room temperature 40 tamed 1S i washed Wlth. i of methanol and with stirring allowed to air dry for /2 hour; it weighs 20.1 g. (45.6%).

When the reaction mixture has cooled to room tem- EX MPL l0 perature (40 C. or lower), the gases r Vented and The procedure of Example 6 is repeated using in four P P igig g i fggg g g ggg 32:33:12 5 3252222 diifereritexperiments the following materials instead of added o one liter of Water The aqueous mixture is ElCfitOllltl'llCi hutyronitrile, propionitrile, succinonitrile e p c d into a distilling-flask e flask d Com and benzonitrile. In each case advantageous results are obtained. tents are heated employing a heating mantle. At 76 C. EXAMPLE 11 Cr(CO) is observed to steam distill. Heating is continued for 1.5 hours to insure complete sublimation and A one'hter surfed autoclave is charged With steam distillation, at which time the aqueous mixture is (0-05 H101) of tungsten hexachloridea H101) cooled. The CMCOM afielfilt ti is Washed with of iodine and 250 ml. of acetonitrile. After purging with 50 m1 0 in three Separate washings The CMCOM CO, the veseel is charged to 3000 p.s.i.g. with CO and is then Washed with 50 ml. Et O to remove the MeOH. heatefi, Wlth stirring to 2000 this Point the P The c is removed f the Buchner funnel h sure 15 brought to 5000 p.s.i.g. by charging 600 p.s.i.g. placed in porcelain drying dish aihdried i helm of hydrogen. As the pressure drops it is returned to 5000 The yield of Cr(CO) is 37 g., 84% of theory, p.s.1.g. by addition of another 400 p.s.i.g. of hydrogen.

Using the general procedure f the foregoing example, After heating at 200 C. for five hours, the vessel is aladditional illustrative experiments are indexed comparalowed to 9001 to mom temperature: Vented and p tive'ly as iollows: The contents are added to one liter of water in a dis- Hi CO tilling flask which is heated until steam. distillation of the ClCla I: Cr(CO)g,400-600ml. oHiGN CHZCN 1 Carbon/chromie oxide weight ratio0.165.

Initial charge Total pressure Solid reactants Initial after reaction per moles Reac- Cr(CO) i, 131;. ignilp). tigietonition Time yield Hi 00 p.s.i.g. 0. Ii CrCla learn) 0% (hrs') percent (p.s.i.g.) (p.s.i.g.)

1 2:: 3:288 5:288 it 21288 it 8:? 81% 288 383 7* ii 4--.- 6, 000 5,600 30 5,200 30 0.3 0.2 400600 200 s 84 5 2,100 5,600 42 5,300 32 0.3 0.2 500 200 7 s5 0."- 3,100 5,600 20 5,200 27 0.3 0.2 500 200 5.5 03

1 The indicated quantity of H2 is gradually charged to reactor after reaction temperature increases to 200 C.

1 60.5% OHaCN and 87.0% Ii recovere W(OO) appears complete. The white solid is collected on a filter, washed with three 10 ml. portions of methanol and allowed to air dry for one-half hour. This yields 14.6 g. (79%) of W(CO) M.P. 172 C.

EXAMPLE 12 A one-liter stirred autoclave is charged with 27.3 g. (0.1 mol) of molybdenum pentachloride, 63.5 g. (0.25 mol) of iodine and 300 ml. of acetonitrile. After purging with CO, the reaction vessel is charged to 2800 p.s.i.g. with CO and heated, with stirring, to 200 C. At this point, 980 p.s.i.g. of hydrogen is introduced to raise the total pressure to 5000 p.s.i.g. As heating and stirring are continued, the pressure drops and an additional 720 p.s.i.g. of hydrogen is introduced to restore the pressure to 5000 p.s.i.g. After heating for five hours, the reaction vessel is allowed to cool to room temperature, vented and opened. The contents are added to one liter of water in a distilling flask which is heated until the steam distillation of the Mo(OO) appears complete. The white solid is collected on a filter, washed with 30 ml. of methanol and allowed to air dry -for one-half hour. The yield of Mo(CO) M.P. 150 C. (dec.), is 17.8 g. (67%).

EXAMPLE 13 The general procedure of the foregoing examples is repeated except that CrI is used as a source of chromium and iodine. There are combined in an autoclave equipped with an agitator and temperature control means 0.2 mol of Crl in 500 ml. CH CN. The autoclave is pressurized with 5400 p.s.i.g. of CO 30 C. and heated to 200 C. whereupon 36 00 p.s.i.-g. of hydrogen is introduced. The reaction mixture is heated 200 C. with agitation for 6.5 hours. A 93% yield (41.5 g.) of Cr(CO) is obtained via steam distillation of the reaction mixture. 1

EXAMPLE 14 The procedure of Example 1 is reepated using NaI as a source of iodine. There are combined in an autoclave 0.2 mol CrCl and 0.6 mol NaI in 500 ml. of CH CN. The autoclave is pressurized with 5200 p.s.i.g. 25 C.

and is then heated to 200 C. at which time 2300 p.s.i.g. of hydrogen is introduced. The reaction mixture is maintained at 200 C. for 6.5 hours. After steam distillation the yield of Cr(CO) is 59% (26.0 g.).

EXAMPLE 15 EXAMPLE 16 A two liter autoclave is charged with 10.4 g. (0.2 mol) finely-divided chromium metal (99% pure, 100 mesh), 76.0 g. (0.3 mol) iodine, and 500 ml. of acetonitrile. The autoclave is pressurized to 5300 p.s.i.-g. with CO. and heated to 200 C. for 5 hours. During the 5 hour heating period, 3400 psi-g. of H is charged to the autoclave to maintain a pressure not less than 9600 p.s.i.g. and not greater than 10,000 p.s.i.g. After the vessel has cooled to room temperature, the reaction mixture is added to one liter of H 0 and heated. The Cr(CO) steam distills and is separated from the liquid portion by filtration. After washing the Cr(CO) with 30 ml. of MeOH and 30 ml. of ethyl ether, it is found to weight 34.1 g. (77% yield based on Cr metal).

EXAMPLE 17 The procedure of Example 3 is repeated using propio- 6 nitrile instead of acetonitrile. A 45% yield of Cr(CO) is obtained.

It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited, since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

What is claimed is:

1. A process for preparing a carbonyl of a metal selected from the group consisting of chromium, tungsten and molybdenum which comprises introducing into a pressure reactor a metal source selected from the group consisting of the metal per se, trivalent chromium compounds, divalent chromium compounds, tungsten hexachloride, and molybdenum pentachloride; a substance selected from the group consisting of iodine and iodine containing compounds; and a nitrile of the formula R(CN) wherein n is a number from 1 to 2, inclusive, and R is selected from the group consisting of lower alkyl, phenyl and lower alkylene; in the absence of any reducing metal; pressurizing the reactor with carbon monoxide to a pressure in the range of about 1000 to 10,000 p.s.i.g.; the ratios of reactants being at least 0.1 mole of iodine, 3 moles of nitrile and 6 moles of carbon monoxide per mole of metal source; heating the reactor to a temperature of about 150 to 325 C. and maintaining the temperature until the reaction is completed as evidenced by a pressure drop corresponding to the utilization of carbon monoxide; and separating the thus formed carbonyl of said selected metal by filtration and steam distillation.

2. The process of claim 1 wherein an amount of hydrogen is added which is suflic-ient to increase the pressure within the reactor about 2000 p.s.i.g. at 200 C., the weight ratio of hydrogen to carbon monoxide being no greater than 1:1.

3. The method according to claim 1 wherein the iodine is pnovided by using as the metal source an iodide of the metal.

4. The process according to claim 1 wherein the metal source is the metal per se.

5. The process according to claim 1 wherein the metal source is metallic chromium.

6. The method according to claim 1 wherein the metal source is chromium ore.

7. The process according to claim 1 wherein the metal source is a. trivalent chromium compound.

8. The process according to claim 1 wherein the metal source is chromium trichloride.

9. The process according to claim claim 1 wherein the metal source is chromic oxide.

10. The process according to claim 1 wherein the metal source is a divalent chromium compound.

11. The process according to claim 1 wherein the metal source is the iodine-containing compound Crl 12. The process according to claim 1 wherein the metal source is metallic tungsten.

13. The process according to claim 1 wherein the metal source is tungsten hexachloride.

14. The process according to claim 1 wherein the metal source is metallic molybdenum.

15. The process according to claim 1 wherein the metal source is molybdenum pentachloride.

16. The process according to claim 1 wherein the nitrile is acetonitrile.

17. The process according to claim 1 wherein the nitrile is propionitrile.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 100,687 August 13 1963 John H. Wotiz It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 39 and -10 strike out "in the absence of any reducing metal." and insert instead The expression in the absence of any reducing metal" as employed in the specification and claims is intended as meaning that none of the commonly known reducing metals are added. This expression, however, is not intended to exclude the possibility of any of the reactants or materials present in the reaction performing the function of a reducing I ge t. column 2 line 57 for "i.g." read e,g. column 4, line 53 for "veseel" read vessel column 5, line 39 for "reepated" read repeated line 42, after "p. s. i.g. insert CO Signed and sealed this 12th day of May 1964,

(SEAL) Attest:

ERNEST SWIDER EDWARD J: BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR PREPARING A CARBONYL OF A METAL SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, TUNGSTEN AND MOLYDBEUM WHICH COMPRISES INTRODUCING INTO A PRESENCE RECTION A METAL SOURCE SELECTED FROM THE GROUP CONSISTING OF THE METAL PER SE. TRIVALENT CHROMIUM COMPOUNDS, DIVALENT CHROMIUM COMPOUNDS, TUNGSTEN HEXACHLORIDE, AND MOLYBDEUM PENTACHLORIDE; A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF IODINE AND IODINE CONTAINING COMPOUNDS; AND A NITRILE OF THE FORMULA R(CN)N, WHEREIN N IS A NUMBER FROM 1 TO 2, INCLUSIVE, AND R IS SELECTED FROM THE GROUP CONSISTING OF LOWER ALKYL, PHENYL AND LOWER ALKYLENE; IN THE ABSENCE OF ANY REDUCING METAL; PRESSURIZING THE REACTOR WITH CATRBON MONOXIDE TO A PRESURE IN THE RANGE OF ABOUT 100 TO 10,000 P.S.I.G.; TO RATIOS OF REACTANTS BEING AT LEAST 0.1 MOLE OF IODINE 3 MOLES OF NITRILE AND 6 MOLES OF CARBON MONOXIED PER MOLE OF METAL SOURCE; HEATING THE REACTOR TO A TEMPERATURE OF ABOUT 150* TO 325*C. AND MAINTAINING THE TEMPERATURE OF ABOUT 150* ACTION IS COMPLETED AS EVIDENCED BY A PRESSURE, DROP CORRESSPONDING TO THE UTILIZATION OF CARBON MONOXIED; AND SEPARATING THE THUS FORMED CARBONYL OF SAID SELECTED METAL BY FILTRATION AND STEAM DISTILLATION. 